Back draft safety device for jacketed gas-heated liquid heaters



Jan. 2, 1968 G. HEIN ETAL 3,361,127

BACK DRAFT SAFETY DEVICE FOR JACKETED GAs-HEATED LIQUID MEATERSv Filed May 2, 1966 m M M E W M V q l l l l l l Il 1 h V f/ MY m m B f Il m. n lul n w v /m n m\\ m AMW V IJ J n .l Il. X I IIIIQFkII/IU|I|IJWI| Ill/III im .1 j, k r T Il l| u v w ,s lllll I1 r llllll NME mi /1 United States Patent O 3,361,127 BACK DRAFT SAFETY DEVICE FOR JACKETED GAS-HEATED LIQUID HEATERS Georg Hein, Huckeswagen, and Gernot Rottmann, Solingen, Germany, assignors to Joh Vaillant KG, Remscheid, Germany Filed May 2, 1966, Ser. No. 546,902 Claims priority, application Germany, May 3, 1965, V 28,375 4 Claims. (Cl. 126-307) ABSTRACT F THE DISCLOSURE A back draft safety device is provided for use in the jacket of a gas appliance which has front and rear walls connected by side walls, the side walls having lateral outlets. The device is positioned above the burner and lateral outlets. It comprises a horizontal baille, which is U-shaped in cross section and which extends between the front and rear walls below the top ilue connection on the jacket and above the lateral outlets. Two shields extend upwardly from the -bafile and transversely thereto. One shield is positioned a given distance away from the rear wall of the jacket and the other shield is positioned the same distance away from the front wall. The shields have a length as measured parallel to the front and rear walls of at least three times the width of the baille as measured in the same direction.

This invention relates to a back draft safety device which is disposed internally of an appliance jacket of a gas-heated liquid heater, provided with lateral outlets. Back draft conditions occur when wind blows into the ilue chimney from above. Back draft safety devices are known which direct the back draft together with the rising heating gases to the lateral outlets of the appliance jacket and prevent the back draft from passing into the combustion chamber. To achieve this, the back draft safety device is formed with a baille arranged between the front wall and the backwall in the vicinity of the ilue connecting socket, whereby the back draft is diverted to the lower lateral outlets. When no back draft is present, the rising heating gases ilow around the baille.

However, in such back draft safety devices the rising heating gases are not suiciently carried along when a back draft is present and combustion is noticeably impaired. This is apparently due to the fact that in prior art back draft safety devices of the type indicated back draft and ilue gas current do not contact each other on a suillciently large area. If it is imagined that back draft and countercurrent flue gas current were solid ilow bodies, they would contact each other only on the front surfaces facing each other. This, however, is not suflicient to provide for such an intimate contact between the back draft and the ilue gas current that the flue gas current will be carried along by the back draft and directed towards the outlets.

It is therefore the object of this invention to design the back draft safety device in a manner such that there will be produced larger contact surfaces between back draft and ilue gas current, that is, that the ilow bodies of the back draft and of the ilue gas current do not only contact each other on the front surfaces thereof, but also on the vertical side surfaces.

According to the invention this object is being attained by providing that shields project beyond the baille. These shields are arranged parallel to the front wall and back wall and spaced therefrom. These shields are effective to restrict the back draft impinging on the baille in its eX- tenr between front wall and back wall so that the ilue gases may still rise in front of and behind the Ipartial 3,361,127 Patented Jan. 2, 1968 ICC back drafts divided -by the baille and diverted towards the lateral outlets and thereby obtain better contact therewith. It has shown that certain residual ilue gas portions still ilow upwardly forwardly and backwardly of the partial back drafts, ilowing between the shields and the front wall and the back wall, respectively. These residual portions are also drawn in by the back draft over the upper edges of the shields and are entrained thereby. It has shown that by these shields restricting the back draft in one dimension an unobjectionable exhaust of the rising ilue gases is obtained. Expediently, the length of the shields corresponds at least to three times the width of the baille so that the shields also project laterally from the baille far enough so as to achieve an eilective restriction of the back draft.

An embodiment of this invention is more fully described hereinafter with reference to the schematic drawings, wherein FIG. 1 illustartes schematically the back draft safety device in elevation;

FIG. 2 illustrates a side elevation View thereof.

A fin block 1 through which water tubes extend, constitutes the head of a heating section 2 in which heating `gases rise and are in heat exchange with the water ilowing through the iln block 1.

Above the iin block 1 internally of an appliance jacket 3 which jacket is formed with lateral outlets 3', there is disposed a back draft safety device 4 carrying a ilue gas connecting socket 4" above inclined guiding surfaces 4. Between the front wall 5 and the back wall 6 of the back draft safety device and closely below the ilue gas connecting socket 4 a baille 7 is mounted in web-like manner. Baille 7 has turned up edges 7. Shields 8, 8' pro- Jiect beyond the baille 7. Shields 8, 8 are positioned parallel to the front wall and back wall (5, 6) at a distance a. The length of the shields 8, 8 corresponds at least to three times the width of the baille 7 so that the shields 8, 8 project laterally from the baille 7. As is indicated by the dash-dotted showing, the shields 8, 8 may be provided in such length that they join the inclined guiding surfaces 4. The back draft safety device also has deilector plates 9 which extend upwardly of the fin block 1. These divert the flue gas issuing from the iin block 1 from the outlet openings 3. Under normal conditions, thus, when there is draft present in the ilue pipe 10, the ilue gas will ilow around the baille 7, without the flow resistance being substantially increased thereby. However, when due to unfavorable wind conditions a back draft will issue from the ilue pipe 10, such back draft will impinge on the baille 7 between the shields 8, 8. These shields 8, 8 prevent the back draft from expanding along the baille 7 towards the front wall 5 and the back wall 6. Instead the back draft is cut by the shields 3, 8', divided by the baille 7 and diverted over the edges 7' towards the outlets 3 of the appliance jacket without contacting the front wall 5 and the back wall 6. These partial back drafts carry away a portion of the rising flue gas. However, since the ilue gas may still rise along the front wall 5 and the back wall 6 in a thickness of layer corresponding approximately to the distance a forwardly and backwardly of the back drafts, the contact area between the partial back drafts and the rising ilue gas layer is increased so that a greater amount of ilue gas is deverted by the back drafts and entrained towards the outlet openings 3. A portion of the ilue gas still passes beyond the baille 7 into the space deilned on the one hand by the shields 8 and 8', respectively and the front wall 5 and the back wall 6, respectively. This portion of the ilue gas current will be drawn in by the back draft over the upper edges of the shields 8, 8 and likewise be carried along towards the outlets 3. It has shown that with an arrangement of the type herein described combustion will also not -be impaired if back draft occurs, which proves that an unobjectionable exhaust is obtained, it being essential that this is attained with a back draft safety device which due to the relatively small overall height is housed within the appliance jacket, whereby, thus the conventional back draft safety device consisting of lower hood and upper hood, disposed exteriorly of the appliance jacket, may be fully replaced thereby,

The invention is claimed as follows:

1. In the combination of a gas burner appliance having a jacket including a front wall, a rear wall, side walls connecting the front and rear walls and having lateral outlets therein, and a ue pipe connection at the top and a back draft safety device embodied in said appliance and positioned above said lateral outlets and between the gas burner and the connection, the improvement comprising: said device including a baille extending between the front and rear walls and directly below said connection; a iirst shield having a face positioned transversely to and intersecting the baille, and parallel to and spaced from the front wall; and a second shield having a face positioned transversely to and intersecting the baille and parallel to and spaced from the rear wall; said shields extending upwardly from said baille.

2. In the combination set forth in claim 1, wherein said first shield is a given distance from said front wall and the second shield is the same distance from the rear wall, and the length of the shields as measured parallel to said front and rear walls is at least three times the width of the bale as measured in the same direction.

3. In the combination set forth in claim 2, wherein said baille is approximately horizontal and has upwardly extending flanges along the side edges thereof, said iianges extending upwardly a distance substantially less than the height of the shields.

4. In the combination set forth in claim 1, wherein said baille is approximately horizontal and has upwardly extending flanges along the side edges thereof, said flanges extending upwardly a distance substantially less than the height of the shields.

References Cited UNITED STATES PATENTS 2,031,314 2/1936 Hunter 126-307 2,487,776 ll/l949 Cartter 126-307 X 2,591,235 4/1952 Cartter 126-307 X 2,703,569 3/1955 Yarbough 126-307 FOREIGN PATENTS 531,032 8/1931 Germany.

FREDERICK L. MATTESON, IR., Primary Examiner.

E. G. FAVORS, Assistant Examiner. 

